From: Roman Gushchin guro@fb.com
commit d87f639258a6a5980183f11876c884931ad93da2 upstream.
Since commit a8ac900b8163 ("ext4: use non-movable memory for the superblock") buffers for ext4 superblock were allocated using the sb_bread_unmovable() helper which allocated buffer heads out of non-movable memory blocks. It was necessarily to not block page migrations and do not cause cma allocation failures.
However commit 85c8f176a611 ("ext4: preload block group descriptors") broke this by introducing pre-reading of the ext4 superblock. The problem is that __breadahead() is using __getblk() underneath, which allocates buffer heads out of movable memory.
It resulted in page migration failures I've seen on a machine with an ext4 partition and a preallocated cma area.
Fix this by introducing sb_breadahead_unmovable() and __breadahead_gfp() helpers which use non-movable memory for buffer head allocations and use them for the ext4 superblock readahead.
Reviewed-by: Andreas Dilger adilger@dilger.ca Fixes: 85c8f176a611 ("ext4: preload block group descriptors") Signed-off-by: Roman Gushchin guro@fb.com Link: https://lore.kernel.org/r/20200229001411.128010-1-guro@fb.com Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/buffer.c | 11 +++++++++++ fs/ext4/inode.c | 2 +- fs/ext4/super.c | 2 +- include/linux/buffer_head.h | 8 ++++++++ 4 files changed, 21 insertions(+), 2 deletions(-)
--- a/fs/buffer.c +++ b/fs/buffer.c @@ -1336,6 +1336,17 @@ void __breadahead(struct block_device *b } EXPORT_SYMBOL(__breadahead);
+void __breadahead_gfp(struct block_device *bdev, sector_t block, unsigned size, + gfp_t gfp) +{ + struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp); + if (likely(bh)) { + ll_rw_block(REQ_OP_READ, REQ_RAHEAD, 1, &bh); + brelse(bh); + } +} +EXPORT_SYMBOL(__breadahead_gfp); + /** * __bread_gfp() - reads a specified block and returns the bh * @bdev: the block_device to read from --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4690,7 +4690,7 @@ make_io: if (end > table) end = table; while (b <= end) - sb_breadahead(sb, b++); + sb_breadahead_unmovable(sb, b++); }
/* --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4207,7 +4207,7 @@ static int ext4_fill_super(struct super_ /* Pre-read the descriptors into the buffer cache */ for (i = 0; i < db_count; i++) { block = descriptor_loc(sb, logical_sb_block, i); - sb_breadahead(sb, block); + sb_breadahead_unmovable(sb, block); }
for (i = 0; i < db_count; i++) { --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -189,6 +189,8 @@ struct buffer_head *__getblk_gfp(struct void __brelse(struct buffer_head *); void __bforget(struct buffer_head *); void __breadahead(struct block_device *, sector_t block, unsigned int size); +void __breadahead_gfp(struct block_device *, sector_t block, unsigned int size, + gfp_t gfp); struct buffer_head *__bread_gfp(struct block_device *, sector_t block, unsigned size, gfp_t gfp); void invalidate_bh_lrus(void); @@ -319,6 +321,12 @@ sb_breadahead(struct super_block *sb, se __breadahead(sb->s_bdev, block, sb->s_blocksize); }
+static inline void +sb_breadahead_unmovable(struct super_block *sb, sector_t block) +{ + __breadahead_gfp(sb->s_bdev, block, sb->s_blocksize, 0); +} + static inline struct buffer_head * sb_getblk(struct super_block *sb, sector_t block) {